[klib] Implement diagnostics for clashing KLIB signatures

Now, we detect clashing signatures during serialization to KLIB and
report a compiler error if two or more declarations have the same
`IdSignature`

For example, for the following code:
```kotlin
@Deprecated("", level = DeprecationLevel.HIDDEN)
fun foo(): String = ""

fun foo(): Int = 0
```

the compiler will produce this diagnostic:
```
e: main.kt:1:1 Platform declaration clash: The following declarations
       have the same KLIB signature (/foo|foo(){}[0]):
    fun foo(): String defined in root package
    fun foo(): Int defined in root package
e: main.kt:4:1 Platform declaration clash: The following declarations
       have the same KLIB signature (/foo|foo(){}[0]):
    fun foo(): String defined in root package
    fun foo(): Int defined in root package
```

Note that we report this diagnostic during serialization and not earlier
(e.g., in fir2ir) for more robustness, so ensure that we check
exactly the signatures that will be written to a KLIB.
If we later introduce some annotation for customizing a declaration's
signature (e.g., for preserving binary compatibility), this
diagnostic will continue to work as expected.

^KT-63670 Fixed

compiler/testData/diagnostics/klibSerializationTests/signatureClash.diag.txt

@@ -0,0 +1,14 @@
+/foo.kt:7:1: error: Platform declaration clash: The following declarations have the same KLIB signature (com.example.klib.serialization.diagnostics/foo|foo(){}[0]):
+    fun foo(): kotlin.Long defined in com.example.klib.serialization.diagnostics
+    fun foo(): kotlin.String defined in com.example.klib.serialization.diagnostics
+    fun foo(): kotlin.Int defined in com.example.klib.serialization.diagnostics
+
+/main.kt:13:1: error: Platform declaration clash: The following declarations have the same KLIB signature (com.example.klib.serialization.diagnostics/foo|foo(){}[0]):
+    fun foo(): kotlin.Long defined in com.example.klib.serialization.diagnostics
+    fun foo(): kotlin.String defined in com.example.klib.serialization.diagnostics
+    fun foo(): kotlin.Int defined in com.example.klib.serialization.diagnostics
+
+/main.kt:16:1: error: Platform declaration clash: The following declarations have the same KLIB signature (com.example.klib.serialization.diagnostics/foo|foo(){}[0]):
+    fun foo(): kotlin.Long defined in com.example.klib.serialization.diagnostics
+    fun foo(): kotlin.String defined in com.example.klib.serialization.diagnostics
+    fun foo(): kotlin.Int defined in com.example.klib.serialization.diagnostics

compiler/testData/diagnostics/klibSerializationTests/signatureClash.kt

@@ -0,0 +1,20 @@
+// FIR_IDENTICAL
+// RENDER_ALL_DIAGNOSTICS_FULL_TEXT
+
+// FILE: foo.kt
+package com.example.klib.serialization.diagnostics
+
+<!CONFLICTING_KLIB_SIGNATURES_ERROR!>@Deprecated("", level = DeprecationLevel.HIDDEN)
+fun foo(): Long = 0L<!>
+
+// FILE: main.kt
+package com.example.klib.serialization.diagnostics
+
+<!CONFLICTING_KLIB_SIGNATURES_ERROR!>@Deprecated("", level = DeprecationLevel.HIDDEN)
+fun foo(): String = ""<!>
+
+<!CONFLICTING_KLIB_SIGNATURES_ERROR!>fun foo(): Int = 0<!>
+
+fun main() {
+    foo()
+}